In an electrophotographic copying machine, the present invention relates to an image forming apparatus having a developing device which develops an electrostatic latent image using one-component developer composed mainly of non-magnetic toner particles.
Heretofore, developing devices employed one-component developer composed of non-magnetic toner, as one of the developing devices used for an electrophotographic copying device. The developing device employs a rotating cylindrical developing roller the surface of which is relatively coarse. On the surface of this developing roller, one-component developer (toner) is applied. The one-component developer is conveyed to the developing region in the identical direction as the rotation of the image forming body. The developer is also used in non-contact development in which toner is developed non-contactly with the surface of the image forming body. Japanese Patent Publication Open to Public Inspection (hereinafter, Japanese Patent O.P.I. Publication) 7-160109 discloses such a developing method.
In the case of a developing device employing two-component developer, toner and carrier are stirred and mixed. By means of triboelectric charging, a charge is provided to the toner. However, if the stirring means is provided in the container of the developing device, the developing device employing the two-component developer necessarily becomes larger compared with a developing device employing one-component developer.
For an image forming apparatus forming a multi-color image, there is an image forming apparatus in which chargers, image exposure means and plural developing devices respectively housing toner of each color are provided around an image forming body, for example a photoreceptor drum and charging, image exposure and developing are repeated over several rotations of the photoreceptor drum so that multiple toner images are superposed on the photoreceptor drum and the toner images are transferred onto a recording medium for fixing. Since the image forming apparatus requires considerable time for image formation, an image forming apparatus in which plural sets of chargers, image exposure means and developing devices are provided in the vicinity of the photoreceptor drum, a toner image is superposed within one rotation of the photoreceptor drum and a full color image is formed, which is excellent in terms of shortening processing time. However, the apparatus also has shortcomings: since plural sets of chargers, image exposure means and developing devices are provided in the vicinity of the photoreceptor drum, the photoreceptor drum is necessary to be large, causing the overall apparatus also to be a larger size. In addition, defective separation of a recording medium from the photoreceptor drum easily occurs.